Stepping switch



F. R. EDGARTON Aug. 12, 1958 STEPPING SWITCH 3 Sheets-Sheet 1 FiledMarch 24, 1955 V a mm mm g on INVENTOR FRANK R. EDGARTON ATTORNEY 12,1953 F. R. EDGARTON 2,847,534

STEPPING SWITCH Filed March 24, 1955 3 Sheets-Sheet 3 v INVEN TOR.

FRANK R. EDGARTON ATTORNEY STEPPIN G SWITCH Frank R. Edgarton, Webster,N. Y., assignor, by mesne assignments, to General Dynamics Corporation,a corporation of Delaware Application March 24, 1955, Serial No. 496,5059 Claims. (01.200-105 The present invention relates to ratchet drivemechanisms, and more particularly to ratchet drive mechanisms foroperating electric stepping switches or the like.

Electromagnetically operated stepping switches have used various typesof ratchet drive mechanisms in order to impart step-wise movement to theswitch contact brush. One particular form of an electromagneticallydriven stepping switch is referred to as a minor switch and is providedwith a ratchet drive mechanism operated by a stepping magnet forstepping the switch contact brush, or brushes, in one directionfrom anormal starting position to a total possible movement of approximatelyeleven equal and successive steps. The ratchet drive mechanism includesa spring which tends to move the ratchet mechanism and switch contactbrush back in a second direction when it is desired to release the.switch and restore it to its normal starting position. A conventionalratchet retainingpawl normallyengages the ratchet teeth to preventmovement of the ratchet and switch brushes in the second direction backto thenormal position and a release magnet is provided, to disengage theretaining pawl from the ratchet teeth when it is desired to return theswitch to normal. .Such an arrangement does not provide for returningthe switch brush and ratchet mechanism to the normal position by aseries of steps.

It is an object of the present invention to provide an improved ratchetdriving mechanism operable for stepping movements in either of twoselected directions and connected to drive an electric switch brushcontact, or contacts, in accordance with the ratchet stepping movements.

Another object of the present invention is to provide an improvedratchet drive mechanismhaving a simplified single driving pawlarrangement for stepping the ratchet mechanism in either of two selecteddirections.

The invention, in its basic concept, consists of a ratchet membermovable against the tension of a ratchet return spring. A driving pawlis movable towardsthe ratchet member in a manner to engage a ratchettooth andthereby step-wise move the ratchet member in a first directionagainst the tension of the ratchet return spring. A retaining pawl is.provided to normally engage the ratchet member teeth and preventmovement of the ratchet ,memher in a second direction, as a returnmovement, for example, in compliance with the tension of the returnspring. According to the invention, a ratchet shift member is providedto engage the ratchet driving pawl in a manner to cause the ratchetdrive pawl to engage the retaining pawl instead of the ratchetteeth whenthedrive pawl is th reafter moved towards the ratchet member. In suchmanner, the ratchet member is allowed to move in the second direction incompliance with the tension of the return spring so long as theretaining pawlis disengaged from the ratchet teeth by reason of theengagement of the drive pawl with the retaining pawl during the movementof the drive pawl towards the ratchet member.

United States Patent 2,847,534 Patented Aug. 12, 1 7958 In theparticular embodiment of the invention to be described, a preferredarrangement includes an escapement cog wheel and an escapement leveractuated simultaneously with the movement of the drive pawl to limit themotion of the ratchet mechanism in either the first or the seconddirection to an incremental amount for each successive movement of thedrive pawl towards the ratchet member while either in the normal ratchetdriving position or in the shifted ratchet releasing position.

A further feature of the invention, in the preferred form to bedescribed, includes a ratchet shift control mechanism arranged toactuate the previously described shift mechanism whenever the ratchetmechanism reaches a predetermined driven position. For example, afterthe ratchet mechanism has been moved in the first direction by apredetermined number of successive ratchet stepping movements, the shiftcontrol mechanism operates the shift mechanism to cause the next seriesof successive movements of the drive pawlto disengage the retaining pawlfrom the ratchet teeth and thereby produce a series of ratchet steppingmovements in the second or return direction. After a similar movement ofsuccessive return ratchet stepping movements, a shift control mechanismis again operable to return the ratchet shifting mechanism to the normalposition causing the next seriesv of successive ratchet steps to beagain produced in the first direction by reason of the engagement of thedriving pawl with the ratchet teeth.

Further objects, features, and the attending advantages of the inventionwill be apparent with reference to the following specification anddrawings in which:

Fig. 1 is a perspective elevation of the ratchet mechani'sm of theinvention as applied to a stepping switch assembly;

. Fig. 2 is, an exploded view showing the details of the essentialelements of the ratchet drive mechanism ofthe invention;

Fig. 3 is a detailed view of the ratchet mechanism with the drive pawlin a position about to engage the ratchet toothford'riving the ratchetmember in a first direction;

Fig. 4 is a view similar to Fig. 3 but showing the drive pawl at themoment of engaging the ratchet tooth;

Fig. 5 is a view similar to Fig. 3 but with the drive pawl shifted to aposition about to engage the retaining pawl; and

I Fig.' 6 is a view similar to Fig. 5 but showing the drive pawl in theposition of engaging the retaining pawl to allow, a stepping movement ofthe ratchet member in the second direction.

' Referring now to Figs. 1 and 2 of the drawings for a generaldescription of the invention, the ratchet drive mechanism and switchcontact brushes are mounted on a suitable base or frame member 10'. Apivot post 11 is secured to extend perpendicularly from the base 10, as.shown. A ratchet member 12, in the preferred form of. the inventionbeing described, is actually a rotary ratchet wheel rotatably journaledon the pivot post 11, and is provided with a depending shank portion 16to which is secured an escapement cog wheel 13 and a pinion gear 14. Ahelical spring 15 surrounds the lower end 16 of the depending portion ofthe ratchet gear 12. Oneend 17 of the spring 15 is adjustably secured bymeans of the adjusting lock washer 18 and clip19 to the base member 10.The other end 20 of the spring 15 is secured to the depending shank 16of the ratchet gear 12 in any suitable manner such that rotation of theratchet gear 12 in the counterclockwise direction will tendto wind thespring 15. The spring 15 is wound to an initial tension by an adjustmentof the position of the lock washer 18 such that the ratchet gear 12would tend to move in the clockwise direction to a normal or startingposition whenever the retaining pawl, to be described, is disengagedfrom the ratchet gear teeth.

A drive pawl is pivotally journaled at 26 on a driving lever arm 27. inthe preferred embodiment of the invention, the driving lever arm 27 isan extension of the armature 28 of an electromagnet 29. The drivingarmature 28 is pivotally supported at 38 and is normally urged to anouter position relative to the magnet coil 29 by means of the coilspring 31, as is conventional. It should be mentioned that other meansof actuating the ratchet drive pawl 25 may be used in place of theelectromagnet 29, described above. Whenet er the electromagnet 29 isenergized, the armature 28 is attracted to move the drive arm 27 and thedriving pawl 25 towards the teeth of the ratchet gear 12 to impart asingle stepping movement to the ratchet stepping mechanism, which willbe later described in detail.

A second pivot post is fixed to the base member 10 to extendperpendicularly therefrom and at a distance spaced relative to thepreviously described pivot post 11. A ratchet retaining pawl 36 ispivotally journaled on the pivot post 35 and normally urged by thespring 37 to engage the teeth of the ratchet gear 12 and thereby preventclockwise movement of the ratchet gear 12. The coil spring 37 has alower end 38 fixed to the base member 10 in any suitable manner, and anupper end 39 received in the notch 40 of the pivoted retaining pawl 36for purposes of resiliently urging the retaining pawl 36 into engagementwith the teeth of the ratchet gear 12.

The escapement cog 13 is provided with a plurality of spaced cog teeth,such as those shown at and 46. The driving lever arm 27 is provided withan extended end portion 47 to form an escapement lever for engaging thesuccessive ones of the escapement cog teeth 45, 46, etc., whenever thedrive arm 27 and drive pawl 25 are moved toward the ratchet gear 12. Itwill be later described in detail how the escapement lever 47 engagesthe successive escapement cog teeth to limit the stepping movements ofthe ratchet gear 12 in either direction of movement of the ratchetmember and escapement cog.

A ratchet shift lever 50 is also rotatably journaled on the pivot post35. The shift lever 50 is provided with a lower control arm extension,generally shown at 51, to which are fastened coil springs 52 and 53 inan over-center arrangement for maintaining the shift arm 58 in aselected one of two rotatable positions about the pivoted post 35. Withthe shift lever 50 in the position shown in Fig. 1 of the drawings, thedepending end 54 of the shift lever 50 contacts the drive pawl 25 toposition the drive pawl, which is pivoted at 26 on the drive arm 27, ina manner to engage the teeth of the ratchet gear 12 when advancingtoward the ratchet gear. A coil spring 55 is fastened between the upperend of the drive pawl 25 and the drive arm 27 to normally pivot thedrive pawl 25 in a counterclockwise direction to the position as shownin Fig. 1 of the drawings. When the shift lever 50 is moved in acounterclockwise direction from the position shown in Figure 1 of thedrawings, the drive pawl 25 will be moved in a clockwise direction aboutits pivot 26 to a position for engaging a shoulder 56 of the retainingpawl 36, as shown by the dotted lines of Fig. 2 of the drawings. Thus,with the shift lever 50 moved to the counterclockwise position, asdescribed, driving movements of the drive pawl 25 toward the ratchetgear 12 will cause the drive pawl 25 to contact the retaining pawl 36 atthe shoulder 56 instead of the teeth of the ratchet gear 12 thusdisengaging the retaining pawl 36 from the ratchet gear teeth andallowing clockwise motion of the ratchet gear 12 in response to thewound tension of the helical spring 15.

The shift lever 50 may be operated in any suitable manner at any timewhen it is desired to shift the operation of the ratchet drivemechanism. In the preferred form of the invention being described, theshift .4 lever 50 may be operated by either or both of the following twodescribed mechanisms.

The first shift control mechanism to be described is comprised of amagnet coil 60 having a pivoted armature 61 with a free end 62 engaging21 depending portion 63 of the shift lever 50. The mechanical moment inthe arrangement shown is such that the energization of the magnet coil60 to attract the armature 61 will produce clockwise rotation of theshift lever 50 to the position shown in Figure 1 of the drawings.

In order to move the shift lever 50 in a clockwise direction, a secondshift control mechanism including a cam and roller is provided. The camand roller mechanism consists of cam surfaces 64 and 65 on the lower end51 of the shift lever 50 against which is slidably received the camroller 66 of a slidably movable control arm 67. When the control arm 67is moved toward the bottom of the drawing shown in Fig. 2, the camroller 66 is caused to ride out of the cam groove 64 into the cam groove65 causing the clockwise movement of the shift lever 50. On the otherhand, when the control arm 67 is moved upward from the bottom of thedrawing as shown in Figure 2, the cam roller 66 moves from the camsurface 65 into the cam surface 64 permitting the springs 52 and 53 tomove the shift lever 50 in the counterclockwise direction.

A rack gear 68 is slidably journaled on an overhead support rod 69,which is in turn supported on the upstanding flanges 70 and 71 securedto the base 10. The rack gear 68 is provided with gear teeth engagingthe drive pinion 14 so that as the ratchet gear 12 is driven with astep-wise movement in either direction the rack gear 68 iscorrespondingly moved in either direction along the overhead support rod69. One end of the rack gear 68 is journaled on the overhead support rod69 at 72 in a position extending between opposing gears 73 and 74 of thecontrol lever 67. This arrangement is such that as the rack gear 68reaches its lower limit of travel, the ear 73 of the control lever 67 isengaged to move the control lever 67 and cam roller 66 into engagementwith the cam surface 65, thus pivoting the shift lever 50 in a clockwisedirection and allowing the drive pawl 25 to pivot to a position forengaging the ratchet gear teeth. Subsequent driving movements of thedrive pawl 25 will cause counterclockwise rotation of the ratchet gear12 and advance the gear rack 68 in the direction away from the lowerportion of the drawings. When the rack gear 68 reaches the upper limitof its travel, the ear 74 of the control arm 67 will be engaged to movethe cam roller 66 back into the cam surface 64, thus pivoting the shiftlever 50 in a counterclockwise direction and moving the drive pawl 25 toa position for subsequently engaging the retaining pawl 36 in subsequentdriving movements. Thereafter, the ratchet gear will be step-wiserotated in a clockwise direction during each driving movement of thedrive pawl 25 to again move the gear rack 68 toward the lower end of thedrawings as shown in Figure 2.

During the movement of the drive pawl 25 into engagement with either theteeth of the ratchet gear 12 or the shoulder 56 of the retaining pawl36, the escapement lever 47 is moved into a position for engaging atooth of the cog wheel 13, thus limiting the rotation of the ratchetgear 12 in either direction to a predetermined amount as required forthe particular stepping movement to be obtained. The gear rack 68 maycarry a plurality of movable switch contact brushes such as shown at 75-78. Each of the switch brushes 7578 may engage successive ones of aplurality of bare wire contacts such as the one indicated on Figure l ofthe drawings at 80. Each of the bare wire contacts is spaced fromanother bare wire contact by an amount equal to the movement of the gearrack 68 by each stepping movement of the ratchet drive mechanism, asdescribed.

Reference will now be made to Figures 36 of asamsss re n the drawingsfor a more detailed description of the operation of the ratchet drivemechanism of the invention. In Fig. 3 of the drawings, the drive arm 27'and drive pawl 25 are shown in the position about to engage a tooth ofthe ratchet gear 12 when the drive pawl 25 s moved towards the ratchetgear 12. The shift lever 50 1s shown in its extreme clockwise positionwith the shift control arm 67 in the lower position and the gear rack 68also in the extreme lower position. Thus, the parts are shown in theposition at the moment of shift of the shift lever 50 to the extremeclockwise position. In Fig. 4 of the drawings, the drive arm 27 is shownin the pos1tion as attracted by the magnet coil 29 with the drive pawl25 engaging a tooth of the ratchet gear 12 and the escapement lever 47contacting a teeth 46 of the escapement cog 13. Thus the gear rack 68 ismoved upward by an incremental stepping amount as determined by thegeometric arrangemente of the rack gear 12 and the escapement cog 46.The actual position of the parts shown in Fig. 4 of the drawings is aposition which assumes that the rack gear 68 has already been steppingupward a number of successive steps from the position shown in Figure 3of the drawings.

When the rack gear 68 has been stepped a predetermined number of stepsupward to the position shown n Figure 5 of the drawings, the shiftcontrol lever 67 s moved upward, moving cam roller 66 towards camsurface 64, allowing spring 53 to pivot the shift lever 50 in acounterclockwise direction thereby pivoting the drive pawl 25 to theposition shown where it will engage the shoulder 56 of the retainingpawl 36 on subsequent driving movements of the drive arms 27. Figure 6of the drawings shows the parts intheposition assumed when the drivearms 27 is attracted by the magnet 29, while the shift arm 50 and drivepawl 25 are in the position to disengage the ratchet retaining pawl 36from the teeth of the ratchet gear 12. The clockwise movement of theratchet gear 12, in response to the wound tension of the helical springwhile the retaining pawl 36 is disengaged from the teeth of the ratchetgear 12, is limited by engagement of the escapement lever 47 with thecog tooth 45. Again it is assumed anumber of successive steppingmovements of the ratchet gear 12 in the clockwise direction have beenperformed to move the gear rack 68 to the intermediate position shown byFigure 6 of the drawings.

While the ratchet drive mechanism of the invention has been specificallydescribed in connection with a preferred embodiment employing arotatable ratchet gear, it should be understood that the principles ofthe inven tion may be applied to a ratchet drive mechanism of the typeembodying a linearly moved ratchet element or gear. In such anarrangement, of course, the helical spring 15 would be replaced with acoil spring or other suitable energy storing device for urging theratchet element to move in one direction opposite to the drivendirection as provided by the positively actuated driving pawl. It shouldalso be apparent that the particular type of control mechanism foractuating the driving pawl shift lever is a preferred form and thatother means for moving the shift lever such as an electromagnet or thelike may be provided, as would occur to anyone skilled in the art,within the spirit of the invention. Various modifications may be madewithin the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A stepping switch comprising, a movable switch contact, a ratchetgear, means interconnecting said contact and said gear for moving saidcontact as said gear is moved, an escapement cog having a plurality ofspaced cog teeth on its periphery, said gear and said cog being securedtogether, means including a spring and disposed for tensioning saidspring as said gear and cog assembly is moved in a first direction andto urge movement of said gear and cog assembly in a second direction, adrive a pawl, a retaining pawl, resilient means to urge said retainingpawl into'engagement with the toothed surface of said ratchet gear tothereby prevent second direction motion of said gear, means for movingsaid drive pawl to and from said ratchet gear to engage a ratchet toothand impart first direction motion to said gear and tension said spring,escapement lever means disposed for engaging a cog tooth of said cogduring first direction movement of said gear to thereby limit the firstdirection movement of said gear for each movement of said drive pawltowards said ratchet gear, and shift means movable from a normalposition to a second position for engaging and moving said drive pawl toa position for engaging said retaining pawl as said drive pawl is movedtowards said ratchet gear and thereby disengage said retaining pawl fromthe toothed surface of said ratchet gear to permit said gear to move inthe second direction by the tension of said spring, said escapementlever means being disposed for engaging a cog tooth of said cog duringsecond direction movement of said gear to thereby limit the amount ofsecond direction movement of said gear for each movement of said drivepawl into engagement with said retaining pawl.

2. A stepping switch comprising, a movable switch contact, a ratchetgear, means interconnecting said contact and said gear for moving saidcontact as said gear is moved, means including a spring and disposed fortensioning said spring as said gear is moved in a first direction and tourge movement of said gear in a second direction, a drive pawl, aretaining pawl, resilient means to urge said retaining pawl intoengagement with the toothed surface of said ratchet gear to therebyprevent second direction motion of said gear, means for moving saiddrive pawl to and from said ratchet gear to engage a ratchet tooth andimpart first direction motion to said gear and tension said spring,shift means movable from a normal position to a second position forengaging and moving said drive pawl to a position for engaging saidretaining pawl as said drive pawl is moved towards said ratchet gear andthereby disengage said retaining pawl from the toothed surface of saidratchet gear to permit said gear to move in the second direction by thetension of said spring, and shift control means for moving said shiftmeans to the second position in response to said ratchet gear beingmoved in said first direction to a first predetermined position and formoving said shift means to the normal position in response to saidratchet gear being moved in said second direction to a secondpredetermined position.

3. A stepping switch comprising, a movable switch contact, a ratchetgear, means interconnecting said contact and said gear for moving saidcontact as said gear is moved, an escapement cog having a plurality ofspaced cog teeth on its periphery, said gear and said, cog being securedtogether, means including a spring and disposed for tensioning saidspring as said gear and cog assembly is moved in a first direction andto urge movement of said gear and cog assembly in a second direction, adrive pawl, a retaining pawl, resilient means to urge said retainingpawl into engagement with the toothed surface of said ratchet gear tothereby prevent second direction motion of said gear, means for movingsaid drive pawl to and from said ratchet gear to engage a ratchet toothand impart first direction motion to said gear and tension said spring,escapement lever means disposed for engaging a cog tooth of said cogduring first direction movement of said gear to thereby limit the firstdirection movement vof said gear for each movement of said drive pawl towards said ratchet gear, shift means movable from a normal position to asecond position for engaging and moving said drive pawl to a positionfor engaging said retaining pawl as said drive pawl is moved towardssaid ratchet gear and thereby disengage said retaining pawl from thetoothed surface of said ratchet gear to per mit said gear to move in thesecond direction by the tension of said spring, and shift control meansfor moving said shift means to the second position in response to saidratchet gear being moved in said first direction to a firstpredetermined position and for moving said shift means to the normalposition in response to said ratchet gear being moved in said seconddirection to a second predetermined position, said escapement levermeans being disposed for engaging a cog tooth of said cog during seconddirection movement of said gear to thereby limit the amount of seconddirection movement of said gear for each movement of said drive pawlinto engagement with said retaining pawl.

4. A ratchet drive mechanism including in combination, a supportingframe, a toothed ratchet gear, an escapement cog having a plurality ofspaced cog teeth on its periphery, said gear and said cog being securedto gether and movably mounted on said frame, means cluding a spring anddisposed for tensioning said sprg as said gear and cog assembly is movedin a first direction t urge movement of said gear and cog assembly in asecond direction, a drive pawl, a retaining pawl, resilient means forurging said retaining pawl into engagement with the toothed surface ofsaid ratchet gear to thereby prevent second direction motion of saidgear, means for moving said drive pawl to and from said ratchet gear toengage a ratchet tooth and impart first direction motion to said gearand tension said spring, escapement lever means disposed for engaging acog tooth of said cog during first direction movement of said gear tothereby limit the first direction movement of said gear for eachmovement of said drive pawl towards said ratchet gear, and shift meansfor engaging and moving said drive pawl to a position for engaging saidretaining pawl as said drive pawl is moved towards said ratchet gear andthereby disengage said retaining pawl from the toothed surface of saidratchet gear to permit second direction movement of said gear by thetension of said spring, said escapement lever means being disposed forengaging a cog tooth of said cog during second direction move-- ment ofsaid gear to thereby limit the amount of second direction movement ofsaid gear for each movement of said drive pawl into engagement with saidretaining pawl.

5. A ratchet drive mechanism including in combination, a supportingframe, a toothed ratchet gear, said gear being movably mounted on saidframe, means including a spring and disposed for tensioning said springas said gear is moved in a first direction and to urge movement of saidgear in a second direction, a drive pawl, a retaining pawl, resilientmeans for urging said retaining pawl into engagement with the toothedsurface of said ratchet gear to thereby prevent second direction motionof said gear, means for moving said drive pawl to and from said ratchetgear to engage a ratchet tooth and impart first direction motion to saidgear and tension said spring, shift means movable from a normal positionto a second position for engaging and moving said drive pawl to aposition for engaging said retaining pawl as said drive pawl is movedtowards said ratchet gear and thereby disengage said retaining pawl fromthe toothed surface of said ratchet gear to permit said gear to move inthe second direction by the tension of said spring, and shift controlmeans for moving said shift means to the second position in response tosaid ratchet gear being moved in said first direction to a firstpredetermined position and to move said shift means to the normalposition in response to said ratchet gear being moved in said seconddirection to a second predetermined position.

6. A ratchet drive mechanism including in combination, a supportingframe, a toothed ratchet gear, an escapement cog having a plurality ofspaced cog teeth on its periphery, said gear and said cog being securedtogether and movably mounted on said frame, means including a spring anddisposed for tensioning said spring as said gear and cog assembly ismoved in a first direction and to urge movement of said gear and cogassembly in a second direction, a drive pawl, a retaining pawl,

resilient means to urge said retaining pawl into engagement with thetoothed surface of said ratchet gear to thereby prevent second directionmotion of said gear, means for moving said drive pawl to and from saidratchet gear to engage a ratchet tooth and impart first direction motionto said gear and tension said spring, escapement lever means disposedfor engaging a cog tooth of said cog during first direction movement ofsaid gear to thereby limit the first direction movement of said gear foreach movement of said drive pawl towards said ratchet gear, shift meansmovable from a normal position to a second position for engaging andmoving said drive pawl to a position for engaging said retaining pawl assaid drive pawl is moved towards said ratchet gear and thereby disengagesaid retaining pawl from the toothed surface of said ratchet gear topermit said gear to move in the second direction by the tension of saidspring, and shift control means for moving said shift means to thesecond position in response to said ratchet gear being moved in saidfirst direction to a first predetermined position and for moving saidshift means to the normal position in response to said ratchet gearbeing moved in said second direction to a second predetermined position,said escapement lever means being disposed for engaging a cog tooth ofsaid cog during second direction movement of said gear to thereby limitthe amount of second direction movement of said gear for each movementof said drive pawl into engagement with said retaining pawl.

7. A reversible ratchet drive mechanism including in combination, asupporting frame, a toothed ratchet wheel, an escapement cog having aplurality of spaced cog teeth on its periphery, a ratchet shaftrotatably mounted on said frame, said wheel and said cog being securedto said shaft, a coil spring, said coil spring being positioned aroundsaid shaft with one end secured to said frame and the other end securedto said shaft in a manner to wind said spring as said shaft is rotatedin a forward di: rection and to cause rotation of said shaft in areverse direction as said spring is unwound, a drive pawl, a retainingpawl, resilient means for urging said retaining pawl into engagementwith the periphery of said ratchet wheel to thereby prevent reverserotation of said wheel, means for moving said drive pawl to and fromsaid ratchet wheel to engage a ratchet tooth and impart forward rotationto said wheel and wind said spring, escapement lever means disposed forengaging a cog tooth of said cog during movement of said wheel in theforward direction to thereby limit the forward rotation of said wheelfor each movement of said drive pawl towards said ratchet wheel, andratchet reversing means for engaging and moving said drive pawl to aposition for engaging said retaining pawl as said drive pawl is movedtowards said ratchet wheel and thereby disengage said retaining pawlfrom the periphery of said ratchet wheel to permit said wheel to rotatein the reverse direction by the unwinding of said spring, saidescapement lever means being disposed for engaging a cog tooth of saidcog during movement of said wheel in the reverse direction to therebylimit the amount of reverse rotation of said wheel for each movement ofsaid drive pawl into engagement with said retaining pawl.

8. A reversible ratchet drive mechanism including in combination, asupporting frame, a toothed ratchet wheel, a ratchet shaft rotatablymounted on said frame, said wheel being secured to said shaft, a coilspring, said coil spring being positioned around said shaft with one endsecured to said frame and the other end secured to said shaft in amanner to wind said spring as said shaft is rotated in a forwarddirection and to cause rotation of said shaft in a reverse direction assaid spring is unwound, a drive pawl, a retaining pawl, resilient meansfor urging said retaining pawl into engagement with the periphery ofsaid ratchet wheel to thereby prevent reverse rotation of said wheel,means for moving said drive pawl to and from said ratchet wheel toengage a ratchet tooth and 9 and impart forward rotation to said wheeland wind said spring, ratchet reversing means movable from a normalposition to a second position for engaging and moving said drive pawl toa position for engaging said retaining pawl as said drive pawl is movedtowards said ratchet wheel and thereby disengage said retaining pawlfrom the periphery of said ratchet wheel to permit said wheel to rotatein the reverse direction by the unwinding of said spring, and shiftmeans for moving said ratchet reversing means to the second position inresponse to said ratchet wheel being rotated in a forward direction to afirst pre determined position and for moving said ratchet reversingmeans to the normal position in response to said ratchet wheel beingrotated in a reverse direction to a second predetermined position.

9. A reversible ratchet drive mechanism including in combination, asupporting frame, a toothed ratchet wheel, an escapement cog having aplurality of spaced cog teeth on its periphery, a ratchet shaftrotatably mounted on said frame, said wheel and said cog being securedto said shaft, a coil spring, said coil spring being positioned aroundsaid shaft with one end secured to said frame and the other end securedto said shaft in a manner to wind said spring as said shaft is rotatedin a forward direction and to cause rotation of said shaft in a reversedirection as said spring is unwound, a drive pawl, a retaining pawl,resilient means for urging said retaining pawl into engagement with theperiphery of said ratchet wheel to thereby prevent reverse rotation ofsaid wheel, means for moving said drive pawl to and from said ratchetwheel to engage a ratchet tooth and impart forward rotation to saidwheel and wind said spring, escapement lever means disposed for engaginga cog tooth of said cog during movement of said wheel in the forwarddirection to thereby limit the forward rotation of said wheel for eachmovement of said drive pawl towards said ratchet wheel, ratchetreversing means movable from a normal position to a second position forengaging and moving said drive pawl to a position for engaging saidretaining pawl as said drive pawl is moved towards said ratchet wheeland thereby disengage said retaining pawl from the periphery of saidratchet wheel to permit said wheel to rotate in the reverse direction bythe unwinding of said spring, and shift means to move said ratchetreversing means to the second position in response to said ratchet wheelbeing rotated in a forward direction to a first predetermined positionand to move said ratchet reversing means to the normal position inresponse to said ratchet wheel being rotated in a reverse direction to asecond predetermined position, said escapement lever means beingdisposed for engaging a cog tooth of said cog during movement of saidwheel in the reverse direction to thereby limit the amount of reverserotation of said wheel for each movement of said drive pawl intoengagement with said retaining pawl.

References Cited in the file of this patent UNITED STATES PATENTS274,325 Himmer Mar. 20, 1883 795,235 Richards et al July 18, 19051,226,966 Goodrum May 22, 1917 1,232,598 Norstrom et a1. July 10, 19172,148,824 Lienzen Feb. 28, 1939 2,277,411 Obszarny Mar. 24, 19422,532,627 Koci Dec. 5, 1950

